Transient Photovoltage Measurements in Nanocrystal-Based Solar Cells

Charge carrier lifetimes play an important role in determining the efficiency of a solar cell but remain poorly understood in nanocrystal-based devices. Carrier lifetimes are often determined using transient photovoltage measurements. Here, we perform transient photovoltage measurements on PbS nanocrystal-based solar cells and determine that the photovoltage decay time cannot be directly interpreted as the carrier lifetime. We show that the decay time can be modeled as the lifetime of an RC circuit, with the resistive component indicating the degree of trap-assisted Shockley-Read-Hall recombination and capacitive contribution coming from the space charge region. These results provide a model with which transient photovoltage data on nanocrystal devices can be analyzed and used to guide device design.